1. Field of the Invention
Generally, the field of the present invention is high power fiber lasers. More particularly, the present invention relates to scalable high power continuous-wave and quasi-continuous-wave fiber lasers.
2. Background
Conventional multi-kilowatt industrial fiber laser systems typically employ a non-scalable architecture consisting of multiple component fiber lasers whose outputs are combined with a fused-fiber signal combiner. The total fiber laser system output power is typically in the range of 2 to 6 kW, and the individual component fiber lasers typically have a power in the range of 0.4 to 1.0 kW. Thus, in order to reach total powers in excess of 1 kW, the outputs from multiple fiber lasers (typically two to ten) must be combined.
Such conventional approaches for achieving a high power fiber laser output have several drawbacks made apparent in light of the present disclosure. For example, by combining the multiple individual fiber laser systems significant redundancy is required in optical, electrical, and mechanical components, thereby increasing the system cost, size, and complexity. In addition, fiber laser component systems generally have limited field serviceability, often requiring replacement of the entire fiber laser component system if an optical component thereof fails. Such entire replacement occurs even when the optical component failure is localized to only a portion of the fiber component system, such as a broken fiber. Requiring the replacement of entire fiber laser component systems increases cost for repair of the complete multi-kilowatt system. Field replacement of a fiber laser component system typically requires highly specialized equipment and clean-room conditions, which are not readily available in factory environments, making service costly and disruptive.
The fused-fiber signal combiner causes optical loss and diminishes the beam quality of the individual fiber laser outputs received. This loss negatively impacts efficiency, which determines power consumption and waste-heat generation, and beam quality degradation can reduce the speed in metal-cutting applications. Furthermore, the signal combiner is expensive, requiring costly equipment and considerable process development and control for fabrication, and it can experience unpredictable variation impacting reproducibility and reliability. Fused-fiber signal combiners are also subject to operational damage, including from optical feedback from the work piece, thereby decreasing system reliability.
Utilizing a signal combiner to achieve up to a few kilowatts of power also limits the ability for laser power of the fiber laser system to be upgraded in the field. For example, a fused signal combiner may include empty ports for receiving additional component fiber lasers. However, the beam quality of output beam is degraded whether or not the extra ports are populated with additional component fiber laser system outputs. Also, if the signal combiner has fully populated input ports, upgrading system output power requires the replacement of one or more of the component fiber lasers with a component fiber laser of higher power. Replacing component fiber lasers is expensive, particularly since there is attendant with it limited or no re-use of the replaced component fiber laser, subsystems, or components.
Conventional system designs are also limited with respect to how technological advances can be accommodated or incorporated since many key components are integrated into each component fiber laser. For example, pump diode technology is advancing rapidly, providing increased power, brightness, and efficiency and reduced cost. Active fibers have also experienced significant technological gains in recent years. Incorporating these advances into an existing fiber laser can be difficult or impossible if the pump diodes, fibers, and electronics are all integrated into a single laser module. For example, the interconnections among components within a single laser module would likely be inaccessible or not easily changeable, and changes to critical components would entail significant design ripple, requiring corresponding changes in the other components. Similarly, the mechanical or thermal designs could be impacted by changing a critical component. Thus, conventional high power fiber laser architectures often must either forgo upgrades based on technological advances or commit to costly and time consuming redesign.
A need therefore exists for a multi-kilowatt fiber laser architecture that minimizes cost by eliminating component redundancy, minimizes or eliminates the drawbacks of signal combiners, is easily and cost-effectively serviceable in the field, enables field upgradability, and is sufficiently flexible to accommodate technological advances without significant cost or design ripple.